1. Field of the Invention
This invention relates in general to antennas, and, in particular, to a multi-mode square horn antenna with cavity suppressed higher order modes.
2. Description of Related Art
Communications satellites are in widespread use. The communications satellites are used to deliver television and communications signals around the earth for public, private, and military uses.
The primary design constraints for communications satellites are antenna beam coverage and radiated Radio Frequency (RF) power. These two design constraints are typically thought of to be paramount in the satellite design because they determine which customers on the earth will be able to receive satellite communications service. Further, the satellite weight becomes a factor, because launch vehicles are limited as to how much weight can be placed into orbit.
Many satellites operate over fixed coverage regions that are geographically limited by the beam coverage and available RF power. The inefficiencies of RF systems, losses due to cabling, and other system constraints limit the available power for the overall system, and, as such, limit the signal strength that is available for communication links. As such, to provide a stable, reliable communications link, the geographic area that is serviced by the satellite must be limited.
Many satellite systems would be more efficient if they contained feed horns that have higher gain or more efficient feed horn systems. However, related art feed horns that have increased efficiency are larger and heavier than standard antennas, and, as such, require larger payload volumes. Further, the increased weight increases launch costs.
There is therefore a need in the art for increased efficiency antenna systems. There is also a need in the art for antenna systems that have increased efficiency feed horns that are of comparable size and weight. There is also a need in the art for antenna systems that provide more complete utilization of space assets without dramatically increasing the cost of manufacturing and operating a satellite. There is also a need in the art for antenna elements in array applications having higher element efficiency such that the number of elements can be reduced. A reduction in the number of elements in an array antenna application reduces the number of feed components and amplifiers, lowers the mass of the system, and reduces cost and antenna complexity.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an antenna apparatus that has an increased efficiency, and a method for increasing the efficiency of multi-mode antenna feed horns.
The method comprises the steps of exciting, within the antenna, a desired transmission mode and an undesired transmission mode of the signal to be transmitted, and converting, within the antenna, power within the undesired transmission mode into power for the desired transmission mode of the signal to be transmitted. An antenna apparatus in accordance with the present invention comprises a feed horn having an input opening, an aperture, and a cavity, disposed between the input opening and the aperture, for suppressing an undesired transmission mode of the antenna and exciting a desired transmission mode of the antenna.
An antenna in accordance with the present invention provides an increased efficiency antenna system. An antenna in accordance with the present invention also provides an antenna system that has increased efficiency feed horns that are of comparable size and weight. An antenna in accordance with the present invention also provides antenna array systems that provide more complete utilization of space assets without dramatically increasing the cost of manufacturing and operating a satellite. Further, an antenna in accordance with the present invention provides antenna elements in array applications that have higher element efficiency such that the number of elements can be reduced.